This is the silver box that sits on top of the exhaust crossover(on manifold) on the passenger side. It has an internal spring that attaches to a rod. This rod activates the choke. See pics. This choke stove attaches to the manifold with one special bolt and unique lock washer. I carry tthis special bolt and washer in Stainless Steel under another listing on the page or add as an option with the choke stove at a savings.